Low-permeability sandstone reservoir fluid channeling channel quantitative identification method

Abstract

The invention belongs to the technical field of oilfield development, and discloses a low-permeability sandstone reservoir fluid channeling channel quantitative recognition method. Comprising the steps of data acquisition through layered pressure drop testing, production dynamic well testing, absolute permeability calculation, correlation degree calculation, actual splitting water yield calculation, fluid channeling quantity calculation and fluid channeling channel volume calculation. Reservoir physical property data are obtained through a water injection well layered pressure drop well testing method and an oil well production dynamic well testing method, the water circulation volume difference before and after the fluid channeling channel is formed is calculated so as to represent the development degree of the fluid channeling channel, and profile control measure dosage design can be effectively guided.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield development, and in particular relates to a method for quantitatively identifying crossflow channels in low-permeability sandstone reservoirs. Background Art

[0002] The natural fractures of low-permeability sandstone reservoirs in Jilin Oilfield are poorly developed, and oil wells basically need to be fractured before they can be put into production. Fracturing technology can increase the productivity of single wells, but it will also cause a series of water channeling phenomena such as water cut increase and oil well flooding, which seriously restricts the effect of water drive development. The key to the successful implementation of profile control and water plugging technology lies in the accurate description of the channeling channel. The reasonable amount of plugging agent directly affects the effect of profile control measures. At present, a lot of work has been done on the identification method of channeling channels, mainly including tracer test identification method, production dynamic method, well-to-well connectivity identification method and pipe flow model algorithm. These methods provide certain references for subsequent research, but some methods require complex test data, such as tracer testing and production logging. Due to the limitations of test costs and test cycles, it is often difficult to ensure that each well has comprehensive test data. Some methods ignore the differences in reservoirs before and after the formation of channeling channels, and the changes in seepage characteristics. For example, early logging data only represents initial data, and the reference significance is small as the development continues to change. The quantitative description of crossflow channels is basically a quantitative understanding based on integrated qualitative understanding, such as fuzzy comprehensive evaluation method, correlation theory analysis method, etc., which usually gives weights to logging, dynamic, profile testing, tracer and other technologies, comprehensively evaluates the interpretation results, and divides the severity level. It can only compare the differences between different well layers, and cannot carry out a quantitative description of the scale of fracture crossflow. Summary of the invention

[0003] In order to overcome the deficiency that the existing identification methods cannot quantitatively describe the degree of crossflow, the present invention provides a method for quantitatively identifying crossflow channels in low permeability sandstone reservoirs. The method is based on geological and dynamic data, and takes the stratified pressure drop of water wells and the interpretation of oil well production tests as the core to obtain reservoir parameters. The volume of crossflow channel development in fractures is characterized by the volume of invalid water circulation, which provides a basis for the scientific dosage design of profile adjustment and water plugging.

[0004] The above object of the present invention is achieved through the following technical solution: A method for quantitatively identifying crossflow channels in low permeability sandstone reservoirs, the steps of which are as follows:

[0005] 1. Layered pressure drop test: Carry out shut-in layered pressure drop test on each target water injection well, obtain pressure drop data, and use well test interpretation method to calculate the current water phase permeability Kw2.

[0006] 2. Obtain oil phase permeability: Using the wellhead daily production data and bottom hole pressure data of the oil well in different time periods obtained in step 1, the oil phase permeability Ko1 interpreted in the initial stage of production and the current oil phase permeability Ko2 are obtained through production dynamic well testing methods.

[0007] 3. Calculate relative permeability and absolute permeability: Use the initial water content and current water content of the oil well as reference parameters, and use the flow rate equation (Formula 1) to inversely calculate the relative permeability Kw1 and absolute permeability K of the water phase before the crossflow channel is formed, i.e. at the initial stage of production.

[0008]

[0009] 4. Calculate the correlation coefficient and degree of association: Based on the grey correlation theory, calculate the correlation between oil and water wells, and use the monthly water injection volume of the injection well and the monthly water production volume of the production well as the parent sequence and child sequence for factor comparison. Finally, calculate the correlation coefficient and degree of association between the injection and production wells according to formulas (2) and (3).

[0010]

[0011]

[0012] Where: x i is the monthly water injection volume of the injection well, m 3 ;y i is the monthly liquid production of the production well, m 3 ξ i is the correlation coefficient, r i For the degree of relevance.

[0013] 5. Calculate the actual split water production: Due to the difference in well patterns, a production well will be affected by multiple water injection wells. Its actual liquid production is the result of splitting the liquid production in each injection and production direction. After determining the correlation between oil and water wells in step 4, the liquid production of each production well is split along each injection and production direction according to the correlation to obtain the actual split water production Q rcsl .

[0014] 6. Calculation of crossflow flow: The difference between the actual water production of the production well and the theoretical water production under the condition that there is no crossflow channel in the well group is taken as the daily ineffective water flow between the injection and production wells, which represents the crossflow flow caused by the expansion and extension of the fracture to form a crossflow channel. The calculation method is formula (4) and formula (5).

[0015] Q wxsl =Q rcsl -Q llcsl (4)

[0016]

[0017] Where: Q wxslis the invalid water flow between injection and production, m 3 / d;Q rcsl is the actual splitting water production of the production well along this direction, m 3 / d;Q llcsl is the theoretical water production of the production well, m 3 / d;K rw is the relative permeability of the water phase; K is the absolute permeability, that is, the oil phase permeability under bound water saturation, md; H is the effective thickness of the water-absorbing layer, m; ΔP is the production pressure difference, MPa; μ w is the viscosity of the aqueous phase fluid, mp·s; r i is the fluid supply distance of the production well, m; r w is the radius of the production wellbore, m.

[0018] 7. Calculate the volume of the crossflow channel between injection and production: Substitute the data obtained in step 3 and step 5 into the calculation formula in step 6, and the remaining parameters are daily records, and the daily ineffective flow volume can be obtained. Then, the tracer is used to explain the time of injection in each injection direction or the dynamic response time t of the production well after the injection well changes the working system (such as injection, well stop, increase or decrease of injection volume, measures), and the volume of the crossflow channel between injection and production is calculated according to formula (6).

[0019] V=Q wxsl ×t (6)

[0020] Where: V is the volume of the crossflow channel between injection and production, m 3 ; t is the time it takes for the drug to take effect, d.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: by obtaining reservoir physical property data through stratified pressure drop test of water injection wells and dynamic well test of oil well production, the volume difference of water circulation before and after the formation of the crossflow channel is calculated to characterize the development degree of the crossflow channel, which can effectively guide the dosage design of profile adjustment measures. The identification method is used to guide the implementation of profile adjustment in 25 well groups in Jilin low-permeability oilfield, with an average single well group oil increase of 240t, an improvement of 40% over the previous results, an output-input ratio of >2.0, and a dynamic compliance rate of the well group after adjustment of more than 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0023] Figure 1 It is a flowchart of the execution steps of the method for quantitatively identifying crossflow channels in low permeability sandstone reservoirs of the present invention;

[0024] Figure 2 This is a diagram of the calculation interface of program parameters for the quantitative identification method of crossflow channels in low permeability sandstone reservoirs of the present invention. DETAILED DESCRIPTION

[0025] The present invention is described in detail below by specific examples, but the protection scope of the present invention is not limited. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0026] Example 1

[0027] A method for quantitatively identifying crossflow channels in low permeability sandstone reservoirs, the steps are as follows:

[0028] 1. Carry out shut-in stratified pressure drop test on each target water injection well, obtain pressure drop data, and use well test interpretation method to calculate the current water phase permeability Kw2.

[0029] 2. Using the wellhead daily production data and bottom hole pressure data of the oil well in different time periods obtained in step 1, the oil phase permeability Ko1 interpreted in the initial stage of production and the current oil phase permeability Ko2 are obtained through production well testing.

[0030] 3. Using the initial water content and the current water content of the oil well as the reference parameters, the flow rate equation (Formula 1) is used to inversely calculate the relative permeability Kw1 and absolute permeability K of the water phase before the crossflow channel is formed, that is, at the initial stage of production.

[0031]

[0032] 4. Based on the grey correlation theory, the correlation between oil and water wells is calculated. The monthly water injection volume of the injection well and the monthly water production volume of the production well are used as the parent sequence and child sequence for factor comparison. Finally, the correlation coefficient and correlation between the injection and production wells are calculated according to formulas (2) and (3).

[0033]

[0034]

[0035] Where: x i is the monthly water injection volume of the injection well, m 3 ;y i is the monthly liquid production of the production well, m 3 ξ i is the correlation coefficient, r i For the degree of relevance.

[0036] 5. Due to the difference in well patterns, a production well may be affected by multiple water injection wells. Its actual liquid production is the result of splitting the liquid production in each injection and production direction. After determining the correlation between oil and water wells in step 4, the liquid production of each production well is split along each injection and production direction according to the correlation to obtain the actual split water production Q rcsl .

[0037] 6. The difference between the actual water production of the production well and the theoretical water production under the condition that no crossflow channel is generated in the well group is taken as the daily ineffective water flow between the injection and production wells, which represents the crossflow flow caused by the expansion and extension of the fracture to form a crossflow channel. The calculation method is formula (4) and formula (5).

[0038] Q wxsl =Q rcsl -Q llcsl (4)

[0039]

[0040] Where: Q wxsl is the invalid water flow between injection and production, m 3 / d;Q rcsl is the actual splitting water production of the production well along this direction, m 3 / d;Q llcsl is the theoretical water production of the production well, m 3 / d;K rw is the relative permeability of the water phase; K is the absolute permeability, that is, the oil phase permeability under bound water saturation, md; H is the effective thickness of the water-absorbing layer, m; ΔP is the production pressure difference, MPa; μ w is the viscosity of the aqueous phase fluid, mp·s; r i is the fluid supply distance of the production well, m; r w is the radius of the production wellbore, m.

[0041] 7. Substitute the data obtained in step 3 and step 5 into the calculation formula in step 6. The remaining parameters can be found in the daily production dynamic table to obtain the daily ineffective flow volume. Then, the tracer is used to explain the time for each injection direction to see the agent or the dynamic response time t of the production well after the injection well changes the working system (such as injection, well stop, increase or decrease of injection volume, measures), and the volume of the crossflow channel between injection and production is calculated according to formula (6).

[0042] V=Q wxsl ×t (6)

[0043] Where: V is the volume of the crossflow channel between injection and production, m 3 ; t is the time to see the effect, d. The following table shows the calculation results of a typical well group based on the above identification method.

[0044]

[0045] According to the calculated dosage design, profile control was carried out on 4 water injection wells. All the profile control agents were successfully injected, and the construction pressure rose slowly. After the test, the water injection pressure increased by an average of 1.3 MPa, the average cumulative oil increase for a single well group was 235 tons, and the output-input ratio was above 1.7 at US$45, achieving good application results. The established quantitative identification method for crossflow channels can provide an accurate basis for the dosage of plugging agents in the profile control scheme.

[0046] The above-described embodiments are only preferred embodiments of the present invention, but not all feasible embodiments of the present invention. For those skilled in the art, any obvious changes made thereto without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A method for quantitatively identifying crossflow channels in low permeability sandstone reservoirs, characterized in that: Here are the steps: S1. Layered pressure drop test; S2. Obtaining oil phase permeability; S3. Calculate relative permeability and absolute permeability; S4. Calculate the correlation coefficient and the degree of association; S5. Calculate the actual splitting water production; S6. Crossflow calculation; S7. Calculate the volume of the cross-flow channel between injection and production.

2. The method for quantitatively identifying crossflow channels in low permeability sandstone reservoirs according to claim 1, characterized in that: The step S1 specifically includes: conducting a shut-in stratified pressure drop test on each target water injection well, obtaining pressure drop data, and using a well test interpretation method to obtain the current water phase permeability Kw2.

3. The method for quantitatively identifying crossflow channels in low permeability sandstone reservoirs according to claim 1, characterized in that: The step S2 specifically comprises: using the wellhead daily production data and bottom hole pressure data of the oil well in different time periods obtained by the test in step S1, and obtaining the oil phase permeability Ko1 interpreted in the initial stage of production and the current oil phase permeability Ko2 through the production dynamic well testing method.

4. The method for quantitatively identifying crossflow channels in low permeability sandstone reservoirs according to claim 1, characterized in that: The step S3 specifically comprises: using the initial water content and the current water content of the oil well as reference parameters, and using formula 1 to inversely calculate the relative permeability Kw1 and the absolute permeability K of the water phase before the crossflow channel is formed, i.e., at the initial stage of production; 5. The method for quantitatively identifying crossflow channels in low permeability sandstone reservoirs according to claim 1, characterized in that: The step S4 specifically comprises: calculating the correlation between oil and water wells based on the grey correlation theory, taking the monthly water injection volume of the water injection well and the monthly water production volume of the production well as the parent sequence and the child sequence for factor comparison, and finally calculating the correlation coefficient and correlation between the injection and production wells according to formulas (2) and (3); Where: x i is the monthly water injection volume of the injection well, m 3 ;y i is the monthly liquid production of the production well, m 3 ; ξ i is the correlation coefficient, r i For the degree of relevance.

6. The method for quantitatively identifying crossflow channels in low permeability sandstone reservoirs according to claim 1, characterized in that: The specific step S5 is as follows: due to the difference in well patterns, a production well may be affected by multiple water injection wells, and its actual liquid production is the result of splitting the liquid production in each injection and production direction. After determining the correlation between the oil and water wells in step S4, the liquid production of each production well is split along each injection and production direction according to the correlation to obtain the actual split water production Q rcsl .

7. The method for quantitatively identifying crossflow channels in low permeability sandstone reservoirs according to claim 1, characterized in that: The step S6 specifically comprises: taking the difference between the actual water production of the production well and the theoretical water production under the condition that no crossflow channel is generated in the well group as the daily invalid water flow between the injection and production wells, which represents the crossflow flow caused by the expansion and extension of the fracture to form the crossflow channel, and the calculation method is formula (4) and formula (5); Q wxsl =Q rcsl -Q llcsl (4) Where: Q wxsl is the invalid water flow between injection and production, m 3 / d;Q rcsl is the actual splitting water production of the production well along this direction, m 3 / d;Q llcsl is the theoretical water production of the production well, m 3 / d;K rw is the relative permeability of the water phase; K is the absolute permeability, that is, the oil phase permeability under bound water saturation, md; H is the effective thickness of the water-absorbing layer, m; ΔP is the production pressure difference, MPa; μ w is the viscosity of the aqueous phase fluid, mp·s; r i is the fluid supply distance of the production well, m; r w is the radius of the production wellbore, m.

8. The method for quantitatively identifying crossflow channels in low permeability sandstone reservoirs according to claim 1, characterized in that: The specific step S7 is as follows: the data obtained in step S3 and step S5 are brought into the calculation formula of step S6, and the remaining parameters are daily records, so as to obtain the daily ineffective flow volume. Then, the tracer is used to explain the time of agent exposure in each injection and production direction or the dynamic reaction time t of the production well after the injection well changes the working system, and the volume of the crossflow channel between injection and production is calculated according to formula (6); V=Q wxsl ×t (6) Where: V is the volume of the crossflow channel between injection and production, m 3 ; t is the time it takes for the drug to take effect, d.

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